97 replies to this topic

[Szandor]

For ballistic weapons in general, I would recommend using similar (not necessarily identical) muzzle velocities for modern rough equivalents. For example, as a rough guideline:
AC/2 - M242 Bushmaster 25mm (bonus for being technically classed as an autocannon)
AC/5 - Otobreda 76mm. Also technically an autocannon, but larger with a similar ROF to the bushmaster.
AC/10 - Either 105 or 120mm main gun of modern tanks. 120mm APFSDS slugs from US Abrams tanks are hypersonic, with the "dart" - the actual projectile - traveling around mach 5. Note that this is not technically muzzle velocity, but the speed of the sabot after separation from the petals guiding the projectile down the bore of the weapon.
AC/20 - 155mm howitzer? Of course that's an artillery weapon; not much is larger than a 120 in modern direct-fire weaponry, unless you count the Soviet "Mine's bigger" 125.

As for lasers, there's no point in NOT making them hitscan as the travel time is so negligible. Also I don't understand arguments that hitscan lasers are "too easy"... who here has played mw3 or 4 and always hit what they wanted to with their hitscan lasers? In the heat of battle instant-travel weapons are not pinpoint accurate. Well THEY are, just YOU aren't always. Still need good gunnery skills. Environmental effects? I'd just handwave that... with lasers that powerful and coherent, they'll vaporize anything particulate in their path (snow, rain, dust, sand, fog). Otherwise you'll have to hire a whole development team just to come up with planetary data and adjust beam coherence.

PPCs fire ion streams, similar to modern particle accelerators, only it's one-way instead of a loop. Also remember they have a lot of kinetic impact, not just electrical energy. In all likelihood the beam would be traveling at a pretty good clip, likely similar speed to a high-velocity cannon. Imagine a Gauss rifle, firing a particle beam rather than a slug.

[Logan Solo Sinclair]

Lol dyslexia is a heluva drug... I read "Make all weapons time travel."

[jbone]

Lasers shouldn't ever be lead weapons. It makes it more fun for trying to alpha strike.

[Mautty the Bobcat]

At least in MW4, ballistics weapons have had lead time over distance (less lead for closer range) already. They worked very well in that respect and I would say keep them as they are.

But lasers? No, just plain effing no. Lasers do not have travel time, at all. The only thing I could say to add to lasers is that in the novels I've read they aren't just single point contact weapons, they have a small period of duration over which the damage is minutely spread. This causes the lasers to create gouges and cuts in an enemy mech's armor and not just a single scorched hole.

[Liam]

Strum Wealh, on 24 January 2012 - 04:59 PM, said:

Gauss Rifles fire 113.398kg (0.125t) nickel-ferrous slugs at very high (consistently described as "hypersonic") velocities.
If G.R. slugs are hypersonic, that means they have a muzzle velocity of at least Mach 5.0 (1,710 meters per second).

I saw this and got almost an heart stroke

I do respect some BT values, but some makes really no sense. A weapon that fires a slug with some 100 kg and 1700 m/s would need so much power that it makes no sense from engineering point of view and ith such values it will be an instant kill for "everything". Some hundreds GJ of kin energy ... this means it would need even more to propel that slug, what kind of canon is that?

10 kg would be enough but well ... BT.

EDIT: supposed to be MJ, shame ... anyway some hundreds of MJ are also huge.

Edited by Liam, 07 February 2012 - 11:39 AM.

[Strum Wealh]

Liam, on 07 February 2012 - 06:00 AM, said:

I saw this and got almost an heart stroke

I do respect some BT values, but some makes really no sense. A weapon that fires a slug with some 100 kg and 1700 m/s would need so much power that it makes no sense from engineering point of view and ith such values it will be an instant kill for "everything". Some hundreds GJ of kin energy ... this means it would need even more to propel that slug, what kind of canon is that?

10 kg would be enough but well ... BT.

Standard Gauss Rifles are listed as having 8 rounds (slugs) per ton.
Light Gauss Rifles (introduced by the FWL in 3056) are listed as having 16 rounds (slugs) per ton.
Heavy Gauss Rifles (introduced by the Lyrans in 3061) are listed as having 4 rounds (slugs) per ton.

Also:
Silver Bullet Gauss Rifles (prototypes created by the FedCom in 3051; acquired by the FWL afterward and mass-produced by the Combine in 3078) are listed as having 8 rounds (cluster rounds similar to those used by LB-X autocannons) per ton.
Magshots (available from FedCom starting in 3061) are listed as having 50 rounds (slugs) per ton.
The HAG-40 (introduced by Clan Hell's Horses in 3068) is listed as having 3 shots (bursts of 40 tiny slugs) per ton.
Anti-personnel Gauss Rifles (introduced by Clan Jade Falcon in 3069) are listed as having 40 rounds (slugs) per ton.

We can reasonably assume that they are using metric tons (1000kg/2204.623lbs) as opposed to short/US tons (2000lbs/907.185kg).

On projectile speed:

1.) The novels repeatedly describe Gauss slugs as hypersonic.
Hypersonic → "greater than or equal to Mach 5.0" → "greater than or equal to 1,710m/s"
Examples:
"Twin bolts of azure energy lanced into the humanoid shape before her, followed by a hypersonic Gauss rifle slug." (Sword and Fire; see here)
"A Davion Blackjack pivoted its torso to face him sixty meters away, and McCall triggered his 'Mech's left-arm Gauss rifle. The hypersonic round struck the lighter 'Mech low in the torso and to the left, punching straight through the armor in an explosion of shrapnel and scattering bits of internal circuitry." (Tactics of Duty; see here)
"All eighty-five tons of the BattleMaster shook with recoil as the Gauss rifle fired. The hiss-crack of the hypersonic round firing blended with the bang as the solid shot struck the Mad Cat high on the chest, just beneath the box missile launcher." (BattleTech Starter: Fist and Falcon; see here)

2.) By contrast, the technical readout for the Yellow Jacket gunship (see also: here), a 30-ton attack VTOL deployed in 3050 (according to Solaris7) whose sole weapon is a Gauss Rifle with two tons of ammo, states "This massive weapon, which constitutes the bulk of the craft's weight, can hurl rounds at speeds up to Mach 2.2."
Mach 2.2 = 748.638m/s

Though, the examples in (1) are all fired from 'Mechs, while the example in (2) is fired from an aircraft.
Perhaps the weapon mounted on the aircraft has its power scaled down to allow the aircraft to be able to handle the recoil while in flight, while the 'Mechs, by virtue of being ground-based, can handle increased recoil from having the weapon at a higher power setting?

-----

So, for a Standard Gauss Rifle:

1 ton = 1000kg
(1 ton)/(8 rounds/ton) = 1/8 ton/round = 0.125 ton/round = 125 kg/round
(Where I got the 113.398 figure from the previous post, I don't know... )

For v = 748.638m/s:
KE = 0.5 * 125kg * (748.638m/s)^2 = 3.503x10^7 joules = 35.03 megajoules

For v = 1,710m/s:
KE = 0.5 * 125kg * (1,710m/s)^2 = 1.828x10^8 joules = 182.756 megajoules

For reference:
1 kilowatt-hour = 3.6 megajoules
Using a 60-watt incandescent light bulb for one hour consumes 0.06 kilowatt-hours (0.216 MJ) of electricity. Using a 60-watt incandescent light bulb for 1000 hours (approximate average lifespan of the light bulb) consumes 60 kilowatt-hours (216 MJ) of electricity.

It stands to reason that a Gauss Rifle's capacitors and a BattleMech's fusion engine could handle providing that much energy.

Your thoughts?

[Nik Van Rhijn]

It has always been accepted previously that for all intents and purposes Gauss Rifles are instantaneous, as are effectively PPC's. I can't see any reason why this would change. The longer ranged AC's ie 5 & are presumably higher velocity than the 10 & 20. Given their effective ranges there are no RL weapons that you can equate them with as in RL range goes up with increase in calibre.

[jbone]

And that's assuming a perfect 100 % energy transfer.

But what about calculations for ammo feed, wiring, etc. That eats up some of that ton allocation.

I'd also like to pose that when firing big ole chunks of nickel ferrous slugs you'd probably want to keep them cryogenically cooled since it when your dropping the kind of magnetic forces on that slug to accelerate it form a relative rest to hypersonic speeds when it left the barrel it would be a stream of molten metal not a solid armor shredding solid chunk of love that, on a good shot, means your new mech you just got needs a squeegee and a new head.

SO still let's say it's a 50 kg slug, it still requires a tremendous amount of energy, either way nothing likes to be tapped by a gauss rifle, and besides that Gauss rifles are not exceptionally widespread pre clan invasion. I'm flipping through TRO 3025 and 3026 right now and not seeing the gauss at all (Even the highlander is missing it's signature weapon, but it is in 2750). I'm thinking here and I may be wrong but didn't the gauss rifle get introduced in the to 2750 book, in fact flipping open my ragged copy of the book, the Gauss Makes it's debut from the shadows of 1989 in TRO 2750, and it states it shoots the slug at "Muzzle velocities twice that of conventional weapon systems."

[TheRulesLawyer]

Strum Wealh, on 07 February 2012 - 08:35 AM, said:

For reference:
1 kilowatt-hour = 3.6 megajoules
Using a 60-watt incandescent light bulb for one hour consumes 0.06 kilowatt-hours (0.216 MJ) of electricity. Using a 60-watt incandescent light bulb for 1000 hours (approximate average lifespan of the light bulb) consumes 60 kilowatt-hours (216 MJ) of electricity.

It stands to reason that a Gauss Rifle's capacitors and a BattleMech's fusion engine could handle providing that much energy.

Your thoughts?

I'm going to assume your numbers are correct, but you're only talking energy on target. You're assuming 100% efficiency on launching the projectile. Most likely its going to take far far more energy than that. There is also a huge difference between providing that energy over serveral hours an a few milliseconds.

[Nik Van Rhijn]

Ammo feeds, wiring etc are part of the weapons weight not the ammo. It was re-introduced in 3040 after the Helm Meory Core according to Sarna http://www.sarna.net/wiki/Gauss_Rifle.

[Kaemon]

Zakatak, on 24 January 2012 - 05:23 PM, said:

Okay, so, a Large Laser goes 700m, and it moves at 299'792'460m/s...

...so .000000233 seconds? Ya, lets go ahead and factor that into the game. Everything else in the MW series has some form of travel-time so what's wrong with how things already are?

If you're serious, you just made my computer cry.

If not we rejoice (slowly) and agree.

[Liam]

Strum Wealh, on 07 February 2012 - 08:35 AM, said:

For v = 1,710m/s:
KE = 0.5 * 125kg * (1,710m/s)^2 = 1.828x10^8 joules = 182.756 megajoules

For reference:
1 kilowatt-hour = 3.6 megajoules
Using a 60-watt incandescent light bulb for one hour consumes 0.06 kilowatt-hours (0.216 MJ) of electricity. Using a 60-watt incandescent light bulb for 1000 hours (approximate average lifespan of the light bulb) consumes 60 kilowatt-hours (216 MJ) of electricity.
….
Your thoughts?

well your gauss calculations of kinetic energy with 180 GJ are ok. Your example with bulb is also ok. Still has nothing to do with a weapon system such as coilgun.
Why do you use these stupid mainstream units? I use only W=J/s, you don’t need more fancy stuff like Watthours.

Strum Wealh, on 07 February 2012 - 08:35 AM, said:

It stands to reason that a Gauss Rifle's capacitors and a BattleMech's fusion engine could handle providing that much energy.

You know there are things like W/kg W/m³ etc. if you think you can quench a GW reactor into a mech, you are completely wrong. Let assume us you have one GW reactor, how long you will wait till you can fire this gauss again?

As TheRulesLawyer already said we talk here about to provide a power for some milliseconds.

Edited by Liam, 07 February 2012 - 10:27 AM.

[Strum Wealh]

jbone, on 07 February 2012 - 09:06 AM, said:

And that's assuming a perfect 100 % energy transfer.

But what about calculations for ammo feed, wiring, etc. That eats up some of that ton allocation.

I'd also like to pose that when firing big ole chunks of nickel ferrous slugs you'd probably want to keep them cryogenically cooled since it when your dropping the kind of magnetic forces on that slug to accelerate it form a relative rest to hypersonic speeds when it left the barrel it would be a stream of molten metal not a solid armor shredding solid chunk of love that, on a good shot, means your new mech you just got needs a squeegee and a new head.

SO still let's say it's a 50 kg slug, it still requires a tremendous amount of energy, either way nothing likes to be tapped by a gauss rifle, and besides that Gauss rifles are not exceptionally widespread pre clan invasion. I'm flipping through TRO 3025 and 3026 right now and not seeing the gauss at all (Even the highlander is missing it's signature weapon, but it is in 2750). I'm thinking here and I may be wrong but didn't the gauss rifle get introduced in the to 2750 book, in fact flipping open my ragged copy of the book, the Gauss Makes it's debut from the shadows of 1989 in TRO 2750, and it states it shoots the slug at "Muzzle velocities twice that of conventional weapon systems."

TheRulesLawyer, on 07 February 2012 - 09:14 AM, said:

I'm going to assume your numbers are correct, but you're only talking energy on target. You're assuming 100% efficiency on launching the projectile. Most likely its going to take far far more energy than that. There is also a huge difference between providing that energy over serveral hours an a few milliseconds.

As previously indicated, ammo feeds and such would likely be factored into the weight of the weapon itself, with the weight of the ammo bin itself being negligible.

Also, cryogenic storage of the shells is not only not necessary, but probably detrimental - besides the extra energy cost for the cooling system, having the slugs very quickly go from very, very cold to kinda-warm so quickly would likely cause said slugs to shatter as a result of thermal shock (not to mention the addition the additional stresses in being accelerated to supersonic/hypersonic velocities).

And as far as "Muzzle velocities twice that of conventional weapon systems" goes, the Rheinmetall 120 mm gun used on the M1A1 Abrams MBT has a muzzle velocity of 1,580 to 1,750 m/s (5,200 to 5,700 ft/s) - right around Mach 4.5-ish to 5.0-ish.
Doubling that would give Gauss Rifles a muzzle velocity of 3,160 to 3500 m/s - around Mach 9 to 10 or so...

-----

So, we have our minimum energies needed to launch the projectile.

As far as efficiency:

Quote

Small coilguns are recreationally made by hobbyists, typically up to several joules to tens of joules projectile energy (the latter comparable muzzle energy to a typical air gun and an order of magnitude less than a firearm) while ranging from under one percent to several percent efficiency.

Much higher efficiency and energy can be obtained with designs of greater expense and sophistication. Bondaletov in 1978 in the USSR achieved record acceleration with a single stage by sending a 2-gram ring to 5000 m/s in 1 cm of length, but the most efficient modern designs tend to involve many stages. Above 90% efficiency is estimated for some vastly larger superconducting concepts for space launch. An experimental 45-stage DARPA coilgun mortar design is 22% efficient, with 1.6 megajoules KE delivered to a round.

Though facing the challenge of competitiveness versus conventional guns (and sometimes railgun alternatives), coilguns are being researched for weaponry.

The DARPA Electromagnetic Mortar program is an example of potential benefits, if practical challenges like sufficiently low weight can be managed. The coilgun would be relatively silent with no smoke giving away its position. (Though a coilgun projectile would still create a sonic boom if supersonic, mortars like such are subsonic). Adjustable yet smooth acceleration of the projectile throughout the barrel can allow somewhat higher velocity, with a predicted range increase of 30% for a 120mm EM mortar over the conventional version of similar length. With no separate propellant charges to load, the researchers envision the firing rate to approximately double.

So, let's arbitrarily say that the efficiency of a BT Gauss Rifle is on the order of 20% (not that far off from the 22% efficiency of the DARPA coilgun mortar).

That would quintuple the energy requirements to the range of 175.15 MJ (for Mach 2.2) to 913.78 MJ (for Mach 5.0) to launch a 125 kg projectile that would deliver 35.03 MJ (for Mach 2.2) to 182.76 MJ (for Mach 5.0) of kinetic energy to a target.

At this point, we're still talking less than one gigajoule, and certainly nowhere near the "Some hundreds GJ of kin energy" that so concerned Liam.

Even with a Mach 10 muzzle velocity and lowering the efficiency to ~5%, that only increases our firing energy requirement by 8x, to ~7310 MJ (7.3 GJ)...

And we know that the capacitor bank can be charged for another shot in around 10 seconds... what is the power output, in watts, of a BattleMech-grade fusion engine (whigh is charging the Gauss Rifle's capacitors, in addition to powering the myomers, sensors, other weapons and equipment, and everything else)?

Your thoughts?

Edited by Strum Wealh, 07 February 2012 - 10:31 AM.

[jbone]

The physics of Battletech are powered by this magical thing called plot I guess.. I'm just quoting the original source book, as for the novels, while some of them are good, I point out that what happens in the novels consistently does not hash with the mechanics of battletech.

When these weapons were introduced the discussion about these weapons usually involved large sums of alcohol being consumed during the development, not a lot of physics were discussed. Yes we need hundreds of Megajoules to slam that slug out the barrel of the rifle in question. but how much energy does it take to lift a highlander up into the air and 270 meters horizontally over the course of 10 seconds.

[Liam]

Strum Wealh, on 07 February 2012 - 10:29 AM, said:

At this point, we're still talking less than one gigajoule, and certainly nowhere near the "Some hundreds GJ of kin energy" that so concerned Liam.

supposed to be MJ, as I wrote your calculation was ok (as there stand MJ), no reason here to try to pick on me.
I'm someone who try to clarify and to help and not to criticize.

btw. if you mean this post http://mwomercs.com/...post__p__109563 then you are right, but its because you use points and not commas, was irritating same story for watthour. I used to use commas and J/s in my work.

Strum Wealh, on 07 February 2012 - 10:29 AM, said:

what is the power output, in watts, of a BattleMech-grade fusion engine?

Strum Wealh, on 07 February 2012 - 10:29 AM, said:

And we know that the capacitor bank can be charged for another shot in around 10 seconds...

you are very close

Edited by Liam, 07 February 2012 - 11:36 AM.

[Strum Wealh]

Liam, on 07 February 2012 - 10:55 AM, said:

supposed to be MJ, as I wrote your calculation was ok (as there stand MJ), no reason here to try to pick on me.
I'm someone who try to clarify and to help and not to criticize.

I wasn't picking on you, and if I sounded as such please be assured that it was not my intent to do so.

Liam, on 07 February 2012 - 10:55 AM, said:

you are very close

Well, if we wan to go there...

(7.3 GJ)/(10 seconds) = 7.3*10^8 J/s = ~731.02 megawatts needed to fire a Mach 10 Gauss Rifle every 10 seconds (assuming a 5% efficiency).
(or ~365.51 MW needed for a Mach 5 Gauss Rifle, or ~160.83 MJ needed to fire a Mach 2.2 Gauss Rifle, also assuming a 5% efficiency)

If we bring efficiency back up to 20% (in line with DARPA's Gauss Mortar), the above values are (approximately) quartered.

So...

Quote

The megawatt is equal to one million (10^6) watts. Many events or machines produce or sustain the conversion of energy on this scale, including lightning strikes; large electric motors; large warships such as aircraft carriers, cruisers, and submarines; large server farms or data centers; and some scientific research equipment, such as supercolliders, and also in the output pulses of very large lasers. A large residential or commercial building may consume several megawatts in electric power and heat.

The productive capacity of electrical generators operated by a utility company is often measured in megawatts. On railways, modern high-powered electric locomotives typically have a peak power output of 5 or 6 MW, although some produce much more. The Eurostar, for example, consumes more than 12 MW, while heavy diesel-electric locomotives typically produce/consume 3 to 5 MW. U.S. nuclear power plants have net summer capacities between about 500 and 1300 MW.

The earliest citing of the megawatt in the Oxford English Dictionary (OED) is a reference in the 1900 Webster's International Dictionary of English Language. The OED also states that megawatt appeared in a 28 November 1947 article in the journal Science (506:2).

-----

The gigawatt is equal to one billion (10^9) watts or 1 gigawatt = 1000 megawatts. This unit is sometimes used for large power plants or power grids. For example, by the end of 2010 power shortages in China's Shanxi province were expected to increase to 5–6 GW and the installed capacity of wind power in Germany was 25.8 GW. The largest unit (out of four) of the Belgian Nuclear Plant Doel has a peak output of 1.04 GW.

Though “gigawatt” is usually pronounced today with a hard initial "g", the “j” variant is also accepted.

-----

The terawatt is equal to one trillion (10^12) watts. The total power used by humans worldwide (about 16 TW in 2006) is commonly measured in this unit. The most powerful lasers from the mid-1960s to the mid-1990s produced power in terawatts, but only for nanosecond time frames. The average strike of lightning peaks at 1 terawatt, but these strokes only last for 30 microseconds.

So, the above values for charging one Gauss Rifle are there, but that doesn't necessarily tell us - at least by itself or directly - the power output of any given 'Mech's fusion engine... though, it does imply that they could be in the gigawatt to terawatt range.
Which wouldn't be too bad for a multi-ton bipedal tank/robot thing driven by artificial muscle and powered by a portable fusion reactor, right?

[MaddMaxx]

Wow, gotta love the Physics lads. I was more curious about what materials might be used in a gun that uses 250kg slugs that actually stay together, or do not instantly disintergrate upon leaving the barrel/cannon.

Edited by MaddMaxx, 07 February 2012 - 12:18 PM.

[Liam]

hm well it will be difficult to find an engine that can deliver such power level in a compact cube of some m³. Even fusion power is nice on a paper, but in practice even if it would produce enough energy, there is stuff like cooling, energy conversion etc. it increases size and mass of reactor. 5-30 MW will be probably viable that can be quenched inside of tank some day. Maybe. I hope so. Time will tell.
All these fancy weapons will be implemented in Naval military first, because they have no problems with cooling and most naval ships can be powered by nuclear power, also enough space for capacitor banks. (> current railgun research)

[Black Sunder]

Liam, on 07 February 2012 - 12:24 PM, said:

hm well it will be difficult to find an engine that can deliver such power level in a compact cube of some m³. Even fusion power is nice on a paper, but in practice even if it would produce enough energy, there is stuff like cooling, energy conversion etc. it increases size and mass of reactor. 5-30 MW will be probably viable that can be quenched inside of tank some day. Maybe. I hope so. Time will tell.
All these fancy weapons will be implemented in Naval military first, because they have no problems with cooling and most naval ships can be powered by nuclear power, also enough space for capacitor banks. (> current railgun research)

You're not going to be happy until you get all the real life realism you can get into the game are you? Every post of yours i see its all about realism. Get over it. Stuff in the BT universe works because it just does.

[Logan Solo Sinclair]

Black Sunder, on 07 February 2012 - 03:31 PM, said:

You're not going to be happy until you get all the real life realism you can get into the game are you? Every post of yours i see its all about realism. Get over it. Stuff in the BT universe works because it just does.

I take your point. It obviously is never going to be perfect, at least not for everyone. The way I see it is there are at least three major things that need to be satisfied in the game, whatever gets decided, or has been decided to be in it.

They are;
1.Fun
2.Realism(includes staying true to canon, also more importantly imo true to the original MW/Crescent Hawk games which are sim before fun)
3.What I will arbitrarily call "proper tactical usefulness for anything that goes onto a battlefield"

Balancing these things while obviously not easy(or even possible to do to everyone's satisfaction), is a noble goal, and one that should make for a great game. Every potential players opinion of how they want MWO to be, should be welcomed, 'cause this game deserves to be bigger then WoW, and I would like to see the casual gamer community in on it too.